Washington DC
Very funny Slipry! LOL 
I just hope he was able to separate your humor from the good advice. Here's my 2 cents worth:
1) Search & read the TER reviews. Become a VIP member, if you aren't already, for the full scoop. It's a bargain ($20) relatively speaking. Also, read this discussion board to see who's hot and who's not. That's what I did when I started hobbying last year, and haven't had any bad experiences. It's not rocket science, really.
2) Most locations are hotels, usually average to above average, probably some of the same brands you've stayed in while traveling. There's nothing to fear about going into a hotel--I do it all the time to eat, drink, or use the restrooms. Hotels are, by their nature, full of strangers. When you get the room number, go on up. Feel free to ask for directions from the staff (tho it's probably not necessary); visiting a friend staying there is perfectly fine. If the incall location is a house or apartment, no problem there either. Be sure to arrive a little early, and take traveling delays into consideration. I use Metro 99% of the time. Driving in DC is nuts!
3) Although I've read some reviews in which the two of you shower together, I'd say that's the exception rather than the rule (I've never experienced it). In fact, I don't think I've ever even been asked to shower--I must be a clean looking guy! 
But it's probably not a bad idea to visit the bathroom upon arrival anyway, for some last-minute preparation! Think of it as a date. As far as being robbed while you are in there, if you've selected a quality provider from TER, there's nothing to worry about. I must admit, I considered this when I started hobbying myself, but it's groundless--if you've done your homework here, relax and trust. Showering before leaving isn't a bad idea, either.
Speaking of relaxing, you will probably be nervous the first few times--I was. You'll get over it. I wouldn't recommend drinking a lot to cover it up, though. Slipry, I concur with your last 3 paragraphs, although from what I hear, few guys shave.
It doesn’t hurt to bring some small gift, either, particularly for repeat visits, or if you are nervous and want a way to break the ice. You can bring your own condoms if you like (see post below), but it's not necessary. Tipping isn't necessary, either. Just leave the envelope in plain sight right after you get there, without mentioning it. Just talk and be natural. Be sure to compliment her, too! You might mention that it's your first time.
Be sure to read the FAQ for Newbie board as well (see link). Hope this helps!
Don't know about CA, it's more of a "girls like it, so I do it" sort of thing!
Slipry, use to have the nipple rings too, and a few others too. Unfortunately, had to part with them all except the tongue ring. I'll never give that up...nor would any of my gfs let me. 
From my perspective, I do like ladies who keep it trim. Bare is OK, though a little landing strip is nice (esp. if they already look underaged!) I do them the same courtesy and we end up having lots of fun. If women do keep it au naturale, it makes it challenging for me especially during a 69 (nothing like choking on a hair to ruin the momentum). I would think the same principle would apply to the men.
Sorry to hear about that shower experience.
I hardly ever tip--seems sort of crass to me, although I have a few times. Gifts: perfumes, candy, body splash, wine, etc. Particularly for repeat visits--I ask what they like during my first visit. They always seem impressed.